Allow modules to react before the deletion of a language.
$language: The language object of the language that is about to be deleted.
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_language_delete($language) {
// On nodes with this language, unset the language
db_update('node')
->fields(array(
'language' => '',
))
->condition('language', $language->langcode)
->execute();
}